Researchers from the Institute of Cancer Research (ICR) in London and the University of Southern California (USC) led the largest and the most diverse genetic analysis ever conducted for a prostate cancer study, comprised of more than 200,000 men from countries including the US, UK, Japan, Sweden and Ghana.
'Prostate cancer incidence differs across racial and ethnic groups and it is higher in men of African ancestry and lower in Asian men compared with men of European ancestry' explained co-leader Professor Rosalind Eeles, professor of oncogenetics at the ICR. 'In our new study, we've shown that genetic factors underlie racial and ethnic differences in the incidence of prostate cancer – and by testing for a range of genetic changes, we can identify men of African ancestry who may be at high risk and could benefit from screening.'
Since genetics play an important role in prostate cancer incidence and mortality, researchers believe that including genetic risk scores – a quantitative measure of the genetic predisposition to suffer prostate cancer – could improve the results obtained by the prostate-specific antigen (PSA) test. However, most previous studies and clinical trials on prostate cancer have been focused on white men.
To date, PSA screening is the gold-standard test for the detection of prostate cancer, where high levels of PSA indicate the presence of a tumour. However, most detected prostate tumours are slow-growing and would not need any further treatment – leading to over-diagnosis and over-treatment. In contrast, those patients at high risk of dying from aggressive prostate cancers are not detected early.
In this study, published in Nature Genetics, 86 new genetic variations specific for prostate cancer were discovered, which brings the total known risk variants known to 269. Individually, these genetic variations only have a small effect on the risk of developing prostate cancer, but when many variations are present, the risk can substantially increase. Subsequently, the researchers developed an overall genetic risk score, which they applied to different ethnic and racial groups. They discovered that black men were twice as likely to develop prostate cancer compared to white men of European ancestry. Furthermore, Asian men inherited about three-quarters of the risk of white men.
Prostate cancer is the most common type of cancer in men after skin cancer and the second most common cause of cancer death worldwide. This study is an important step forward in using genetic information to develop more precise and effective screening strategies.
'Our long-term objective is to develop a genetic risk score that can be used to determine a man's risk of developing [prostate cancer],' said corresponding author Professor Christopher Haiman from the Keck School of Medicine at USC. 'Men at higher risk may benefit from earlier and more frequent screening, so the disease can be identified when it's more treatable.'